What is the average age to start your period?

12-13 years: The average age in the United States to have your first period (menarche) is 12.5 years. There is natural variation within the country and across the globe but the average age ranges from 12-14 years. The first signs of puberty are breast development and pubic hair. Finally, menarche is the culmination of a series of events dealing with the maturation of the endocrine system.

12 y: But it also varies, some girls start at age 10y and some as late as. 14y.